The first is a bad idea right off the bat. Paranoia Agent was no fun at all to watch, and the Equestrian version likely won't be any better.
There's already several fics running along the same sort of premise as your second idea. The pony world doesn't really mesh well with any other universe, a rare occurrence in fantasy.
And the last looks like a prequel to Fallout: Equestria. That or it borrows from the rather confusing Lost Universe stories. The gods and demons are...suddenly spaceships? And they manage to hate and try to kill each other as...spaceships? Stuff like that is extremely confusing.
